Standard photoelectric sensors have been utilized extensively in industrial applications. For example, photoelectric sensors have been utilized to raise and/or lower protective gates associated with industrial machinery moving and/or rotating with great rapidity and/or force to prevent the accidental or inadvertent ingress of fingers and/or limbs into these machines while they are operational.
Nevertheless, the performance of a standard photoelectric sensor can be highly dependent upon the color, reflectivity, and texture of the target to be sensed. A standard photoelectric sensor emits light that strikes a target. The amount of returned light must meet a set threshold to determine whether a target is present or not. Poor targets (e.g., dark in color, highly textured, shiny, etc.) may not return enough light to trigger the sensor's output.
A large percentage of photoelectric sensor applications utilize retro-reflective or polarized retro-reflective sensors. These sensors emit a modulated light source that strikes a reflector and returns the light back to a receiver. Anything that comes between the emitter and the reflector blocks the light beam between the emitter and the reflector, thus signaling the presence of the target.
Further, each pixel detected by a photoelectric sensor or image sensor can contain a data point. Accordingly, if there is an image with multiple data points, more than one pixel can influence evaluation of the image. In applications utilizing camera sensor technology, for instance, many image processing algorithms to evaluate images comprising multiple data points are known. Furthermore, in the field of camera sensor technology, where redundancy is a requirement (e.g., in safety systems), multiple cameras can be required.
In single pixel or single beam applications, like background suppression, there is typically only one pixel employed and it is generally not possible to use more than one pixel. Thus, in these applications a rail must be supplied and utilized, and it is not possible to compare more than one pixel. Further, in single pixel applications it can also be difficult to detect shiny objects. Moreover, in these systems there is no possibility to have redundancy without implementing a redundant path.